The present invention relates to a process of filling a container with a filling material wherein the container comprises an outlet valve designed as a check valve, opened by an external action; a device for the preparation and filling of a spontaneously foaming filling material into a container, with a filling material chamber, the volume of which adjusts itself in accordance with a pressure difference between its interior and its surroundings; as well as to a method for its operation.
It is known to fill containers of the above type with the filling material before the check valve is attached, sealing the container. The fact that an intermediate phase is provided between filling the container and sealing application of the valve, during which the filled-in material is exposed to the outside through the container opening, on which then the valve is mounted, and thus can be contaminated, constitutes an essential drawback of these processes: Prevention of possible contamination, such as of filling materials that must be kept sterile, can be ensured only at great expense.
It is an object of the present invention, inter alia, to eliminate this disadvantage in a process of the aforementioned type.
This object has been attained by filling in the filling material through the outlet valve.
If the filling material to be filled in is subjected outside of the valve to a higher pressure than the closing pressure of the check valve, then the latter opens, and the filling material can flow through the valve into the container.
If, in this connection, the pressure in the filling material required for filling is to be reduced, then it is suggested in another embodiment of the process to locate, during filling, the external, opening action, such as by conventionally exerting pressure on a valve cap, at the outlet valve, in other words, to operate the outlet valve as during the subsequent discharging of the filling material, thereby opening this valve.
The above-described conventional filling procedure exhibits special disadvantages, in addition to the aforementioned danger of contamination, for the filling of spontaneously frothing filling materials. These filling materials start frothing as soon as they exit at room temperature into the normal ambient pressure. For this reason, measures must be taken when employing the above-mentioned known procedures for preventing foaming of the filling material in the container at least between filling and the mounting of the outlet valve, actually until the filled-in material has been placed under pressure.
Customarily, the procedure here is such that the liquid filling material component is mixed with the foam gas in a high-pressure tank. During this step, the high-pressure tank with the filling material and the foam gas is cooled down to a temperature at which the spontaneous-foaming activity of the mixing material is greatly reduced even at ambient pressure. In this cooled-down condition, the mixing material is then filled into the container; the low temperature of the material delays frothing within the container during the time between filling and mounting of the outlet valve. Since the time span of the delay is relatively limited, high requirements must be met by this process regarding precision and speed in applying the outlet valve after the filling step. However, ambient pressure is precisely the variable preventing frothing; this pressure can be raised only once the mixing material is in a sealed space, i.e. once the valve has been mounted.
Containers for accommodating such spontaneously frothing filling materials usually comprise an inner container altering its volume as a function of a pressure difference between internal and external pressure, and are designed as twin-chamber containers. The external pressure prevents frothing and acts as a propelling pressure for the discharge of the material. The container comprises, for example, a piston sealingly movable along the inside wall of a can, this piston driven by a spring and/or propellant gas causing the material to move toward the outlet valve, or an inner bag, a propellant gas under pressure being provided between the inner bag and an inner wall of a can which, after filling of the inner bag, drives the material to the outside upon operating the outlet valve. Also the inherent elasticity of such a bag can ensure internal pressure.
By means of a further development of the process according to this invention wherein by application of a corresponding pressure difference the filling material chamber is allowed to collapse to its minimum volume, and a liquid component of filling material is mixed under pressure with a foam gas and is forced under pressure through the outlet valve into the filling material chamber while undergoing volume expansion, the objective is attained that the pressure of the propellant gas, generally pressure of the propellant medium, which prevents frothing, can be provided in the corresponding chamber of the container prior to filling the material chamber, this pressure then increasing further during the filling step. The propellant gas pressure set at the beginning of the filling operation is, however, already sufficient for precluding any frothing.
This ensures that the spontaneously frothing filling material is always maintained under a pressure that prevents frothing, from the instant at which the material is imbued with its self-frothing property, i.e. starting with mixing of the liquid filling material component with the foam gas until and during the filling step; during the filling process, the inner container forms a closed system with a container wherein the mixing step is performed under pressure.
According to the invention, a device for the preparation and filling of a spontaneously foaming filling material into a container with a filling material chamber, the volume of which adjusts itself in accordance with a pressure difference between its interior and its surroundings, comprises a pressure container with a pressure source for producing the internal pressure, a mixer active in the pressure container, and inlets for a liquid filling material and a foam gas into the container, as well as a proportioning means to discharge the filling material, blended with foam gas, under pressure from an outlet.
Although it is definitely possible, under the propulsion action of the pressure in the pressure container, to effect proportioning by corresponding operative control, for example of a block valve, and to generate the pressure in the pressure vessel by using a compressor as the pressure source, it is preferred to utilize at least one piston in the pressure vessel designed as a pressure cylinder as the pressure-generating source and the proportioning device.
Advantageously, the mixer is furthermore designed as a mixing piston.
Due to the fact that a piston rod of the mixing piston slides coaxially in a piston rod tube of the pressure and metering piston, a maximally compact construction of the device is achieved.
It is furthermore suggested to design the piston rod of the mixing piston as a feed pipe for one and/or the other component of the mixing material, this pipe terminating, preferably via a check valve, into the pressure cylinder chamber at the piston face of the mixing piston.
The invention will be described below by examples, referring to figures.